The phosphoinositides are quantitatively minor but metabolically vital constituents of mammalian cell membranes, functioning for instance as the precursors of (a) the intracellular second messenger inositol-1,4,5- trisphosphate, and (b) the protein kinase C activator 1,2-diacyl-sn- glycerol. The overall objective of this proposal is to develop simple and practical general methods for the syntheses of distinct single molecular species of the phosphoinositides, to include phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), phosphatidylinositol-4,5- bisphosphate (PIP2), and their analogs incorporating rational variations in structure based on hypotheses relating structure and biological activity. During Phase I, the feasibility of a composite enzymatic - chemical method of syntheses was tested and demonstrated for the parent phosphoinositide, PI. During Phase II, (1) this method will be adapted and extended to the syntheses of PIP and PIP2, and to selected analogs of PI, PIP and PIP2, (ii) additional complementary approaches will be evaluated and developed to evolve a comprehensive armory of synthetic methods for this group of compounds, and (iii) samples of selected compounds will be prepared for biological assays.